Miss. Code Ann. § 19-1-151

Washington County is bounded by beginning on the Mississippi River, at a point where the line between townships nineteen and twenty intersects the same; thence east on said township line to the line between ranges five and six, west; thence south on said range line to the line between townships sixteen and seventeen; thence east on said township line to the center line of Sunflower River; thence in a southerly direction with the meanderings of Sunflower River and along its center line to the township line between townships fourteen and fifteen; thence west on said township line to the northwest corner of section three, township fourteen, range seven, west; thence south on section lines to the line between townships thirteen and fourteen, at the northwest corner of section three, township thirteen; thence west to the Mississippi River; thence up said river to the beginning. The county site is Greenville.